I wish to find out if there are other ways to put a machine into standby apart from ACPI S2, S3 and S4?With a recent kernel development I discovered that my machine would go into a S3-like mode (not S4) even when there was no power. I have since lost track of this so perhaps someone can remind me what feature this is?

In the conventoinal sense ACPI S3 still consumes around 1% power every hour which I feel is quite a lot.